1. Technical Field of the Invention
The present invention relates to mobile communications systems and, in particular, to a system for scheduling uplink and downlink communications access for packet data communications.
2. Description of Related Art
The next generation of mobile communications systems (comprising, for example, wideband cellular systems) will be required to provide a broad selection of telecommunications services including digital voice, video significantly. This may result in much higher traffic density on the limited communications resources of the system.
In a spread spectrum (code division multiple access) type wideband cellular system, each mobile station has access to its own set of uplink code channels for use in supporting use of the available telecommunications services. These sets of uplink codes between mobile stations, however, due to synchronization concerns, are not experienced as being orthogonal to each other. Accordingly, interference to a limited degree occurs between mobile stations when plural mobile stations simultaneously engage in call communications. In spite of efforts to dynamically control transmit power levels, and thus control interference, this experienced interference may rise to an unacceptable level as an increasingly large number of mobile station calls are processed.
The foregoing interference problem is of special concern in connection with the provision of packet data telecommunications services on the uplink. This is because the traffic being handled by the communications system tends to be very bursty in nature and it is very difficult to predict service access. If a significant number of these uplink bursts occur simultaneously, interference between mobile stations may rise to a sufficient level to impair or block successful communications transmission, not only for the data telecommunications service, but possibly for other telecommunications services as well. There is a need then for a system and method for scheduling mobile station access to the uplink for the purpose of making a packet data communications transmission.
Furthermore, similar concerns exist with respect to interference caused by bursty downlink packet data communications transmissions to mobile station. Thus, there is also a need for a system and method for scheduling base station access to the downlink for the purpose of making a packet data communications transmission.